This invention relates to a shaking machine comprising a frame, a drive mechanism, and at least two supports for the treated matter, which supports are mounted one above the other and are guided and connected to the drive mechanism in a manner such that, in operation, all points of the supports can execute horizontal circular movements at mutually equal velocities and, along paths having mutually equal radii.
Such shaking machines are used, for example, in the cultivation of microorganisms. There, the exchange of substances and, particularly, gases between the microorganisms and the nutrient, substantially depends on the path velocity of the support carrying the matter. If a shaking process is involved requiring a high path velocity, correspondingly high inertia forces, namely centrifugal forces, occur. Thereby, the bearings are highly stressed. In addition, such forces produce tilting moments acting on the frame of the shaking machine and capable of causing uncontrollable rolling motions.
Various designs of shaking machines in which the inertia forces and tilting moments are compensated are already known. For example, Swiss Pat. No. 492,484 discloses a shaking machine comprising a single drive shaft. The drive shaft is provided with a crank acting on the support or supports, carrying the matter, at the center of gravity thereof. The drive shaft is further provided with a counterweight which is located opposite the crank. The counterweight is dimensioned so that the common center of gravity of the support and the counterweight is located on the axis of rotation of the shaft, whereby the centrifugal forces occurring during operation and the torques thereby produced are balanced. This design is advantageous for shaking machines comprising only one support for the matter to be treated. Various drawbacks appear, however, with the use of shaking machines having several supports mounted one above the other.
First, it is necessary to dispose the drive shaft approximately at the center of the machine, so that the shaft must extend through the supporting surfaces of at least those supports which are located below the counterweight. This means that a relatively large area must be left free at the center of the supports. Since, ordinarily, the vessels to be shaken are placed on the supports not individually but in groups on trays, such a necessity results in a great loss of space.
Further, a design with several supports has the disadvantages that the number of supports and their height cannot be varied without particular attention since, otherwise, the common center of gravity of the supports and that of the counterbalance will not lie in the same plane. In view of the fact, however, that the vessels to be shaken frequently have very different heights, it would be very useful in many cases to have the possibility of varying the number of the supports and their spacing.
Another drawback of the mentioned design, is that the uppermost and lowermost supports are located relatively far from the plane of the counterweight. Since, in general, the masses of the vessels placed on the different supports do not exactly correspond to the provided values and frequently also differ from each other, relatively great tilting moments may be produced.
There is also known a shaking machine, disclosed in Swiss Pat. No. 553,009, comprising a plurality of supports for the matter to be treated, and which are carried by a plurality of columns. In this design, the forces are balanced so that the different supports perform circular motions which are dephased relative to each other. Also, the columns are provided laterally of the supports so that the central portions of the supports can be utilized without loss of space. Otherwise, however, this design has drawbacks similar to those of the machine described above, since, again, a satisfactory balancing is obtained only as long as the machine is equipped with the provided number of supports of which each is located at the right level.